This is topic 1972 Mustang Coupe 302 Auto Rear end? in forum Tech Talk at Northern California Ford Owners  .


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Posted by Jdub07 (Member # 2728) on :
 
So did these come stock with a 9" rear or not? How to tell?
 
Posted by blown doors off (Member # 10713) on :
 
I think 8" more flat on top and bottom of pumpkin housing. Google search images should show the differences
 
Posted by Jdub07 (Member # 2728) on :
 
quote:
Originally posted by blown doors off:
I think 8" more flat on top and bottom of pumpkin housing. Google search images should show the differences
Yup flat spot on top and flat spot on bottom of my pumpkin so its an 8". Now i want to know what posi would be good to shove in it?
 
Posted by wilit (Member # 3367) on :
 
Junkyard 8" trac-locs are near impossible to find. Mustang II's or vans are the best bet to find them, but something like less than 5% came from the factory with them. I know in all my years of hunting, I've never found one.

Your best bet is one of these.
http://www.ebay.com/itm/8-Ford-Traction-Lock-Trac-Loc-Posi-Unit-28-Spline-NEW-/390406125230?pt=Motors_Car_Truck_Parts_Accessories&hash=item5ae604b6ae&vxp=mtr
 
Posted by Jdub07 (Member # 2728) on :
 
quote:
Originally posted by wilit:
Junkyard 8" trac-locs are near impossible to find. Mustang II's or vans are the best bet to find them, but something like less than 5% came from the factory with them. I know in all my years of hunting, I've never found one.

Your best bet is one of these.
http://www.ebay.com/itm/8-Ford-Traction-Lock-Trac-Loc-Posi-Unit-28-Spline-NEW-/390406125230?pt=Motors_Car_Truck_Parts_Accessories&hash=item5ae604b6ae&vxp=mtr
I know dick about rear ends (of cars) so what else would i need? or can I just crack open, pull out current 'guts' and bolt this in, refill with fluid and go? I have a 3 speed auto...aren't there ratio's I need to maintain?
 
Posted by Duncan Motors (Member # 7045) on :
 
willit is one of the most helpfull peeps on here, maybe i read wrong, nut hes far from a dick. and no its not a bolt in piece, it will have to be reset up just like any other rear end.
 
Posted by Jdub07 (Member # 2728) on :
 
quote:
Originally posted by Duncan Motors:
willit is one of the most helpfull peeps on here, maybe i read wrong, nut hes far from a dick. and no its not a bolt in piece, it will have to be reset up just like any other rear end.
I "DON'T" know dick......was meant to be typed. I know willit has been a large help to the board along with many others. [patriot]
 
Posted by v-town coupe (Member # 2771) on :
 
quote:
Originally posted by Jdub07:
quote:
Originally posted by wilit:
Junkyard 8" trac-locs are near impossible to find. Mustang II's or vans are the best bet to find them, but something like less than 5% came from the factory with them. I know in all my years of hunting, I've never found one.

Your best bet is one of these.
http://www.ebay.com/itm/8-Ford-Traction-Lock-Trac-Loc-Posi-Unit-28-Spline-NEW-/390406125230?pt=Motors_Car_Truck_Parts_Accessories&hash=item5ae604b6ae&vxp=mtr
I know dick about rear ends (of cars) so what else would i need? or can I just crack open, pull out current 'guts' and bolt this in, refill with fluid and go? I have a 3 speed auto...aren't there ratio's I need to maintain?
yes you can re-gear it for better "out of the hole" acceleration or better "freeway" driving which would mean your cruise rpm would be lower. depending on your tire height and what you consider to be a comfortable rpm to cruise will dictate what type of gears you should go with. if you are running a 26" tall tire out back you will want to be at about 3:00-3:25 ratio to maintain a lower rpm on the freeway with decent acceleration on the street.

I personally have found various 8" pumpkins which were all "open" diffs (non posi) in mustang II cars one I found was a 3:25 setup and the other was a 3:45-3:50 set. both cars that now have these are running posis.

to answer you question "NO" you cant just slap the posi in. you will need to reset the gears which takes some special tools. so if you want to go posi and want better gearing you will need to get both and have them setup or buy the tools and learn how.

hopefully this answers your questions
 
Posted by wilit (Member # 3367) on :
 
quote:
Originally posted by Duncan Motors:
willit is one of the most helpfull peeps on here...
Thanks man I appreciate it, I do what I can...

quote:
Originally posted by Jdub07:
I know dick about rear ends (of cars) so what else would i need? or can I just crack open, pull out current 'guts' and bolt this in, refill with fluid and go? I have a 3 speed auto...aren't there ratio's I need to maintain?
You need some special tools to set up a new carrier in an 8" housing. You'd probably want to take it to a rear end shop to build. It'd probably cost you between $200-$300 depending on where you went.

Gears are extra if you don't want to use your stock gears (probably 2.79's or 3.00's). A set of 8" gears are about $180 from Summit.

[ April 09, 2012, 08:58 PM: Message edited by: wilit ]
 
Posted by Jdub07 (Member # 2728) on :
 
so i'll just get a whole new 3rd member and its a 9" [Smile]
 
Posted by wilit (Member # 3367) on :
 
quote:
Originally posted by Jdub07:
so i'll just get a whole new 3rd member and its a 9" [Smile]
You'll need a new housing cause a 9" 3rd member won't fit in an 8" housing. Most everything else will swap over, axles, brakes, etc.

Honestly if you've got a plain jane 302 and an auto, I wouldn't go with a 9". It's way overkill, slightly more expensive than an 8" and takes more HP to turn than an 8". The 8" is easily good for 450+ rwhp. You'll snap stock 28 spline axles before you break an 8" 3rd member.
 
Posted by Jdub07 (Member # 2728) on :
 
quote:
Originally posted by wilit:
quote:
Originally posted by Jdub07:
so i'll just get a whole new 3rd member and its a 9" [Smile]
You'll need a new housing cause a 9" 3rd member won't fit in an 8" housing. Most everything else will swap over, axles, brakes, etc.

Honestly if you've got a plain jane 302 and an auto, I wouldn't go with a 9". It's way overkill, slightly more expensive than an 8" and takes more HP to turn than an 8". The 8" is easily good for 450+ rwhp. You'll snap stock 28 spline axles before you break an 8" 3rd member.
No i think the car came with a 9"...but maybe it did not maybe the 351 were 9" and the 302 was 8"...haven't cleaned off all the grime and crap to check.
 
Posted by wilit (Member # 3367) on :
 
quote:
Originally posted by Jdub07:
quote:
Originally posted by wilit:
quote:
Originally posted by Jdub07:
so i'll just get a whole new 3rd member and its a 9" [Smile]
You'll need a new housing cause a 9" 3rd member won't fit in an 8" housing. Most everything else will swap over, axles, brakes, etc.

Honestly if you've got a plain jane 302 and an auto, I wouldn't go with a 9". It's way overkill, slightly more expensive than an 8" and takes more HP to turn than an 8". The 8" is easily good for 450+ rwhp. You'll snap stock 28 spline axles before you break an 8" 3rd member.
No i think the car came with a 9"...but maybe it did not maybe the 351 were 9" and the 302 was 8"...haven't cleaned off all the grime and crap to check.
They didn't put a lot of 9" rears in Mustangs. The odds of a car coming from the factory with a 9" is pretty slim. An easy way to tell is get under the car and try and put a socket over the lowest carrier/housing nut. If a socket fits, its an 8", if it doesn't fit, its a 9".
 




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